Signal contribution sections and their use in resistivity studies

Abstract

The electrostatic analogue to direct current resistivity prospecting is employed to construct vertical sections through lines of four electrodes. These show the relative contributions made by individual volume elements of earth to the total potential difference measured between the two potential electrodes. Signal contribution sections enable a comparison of the response of various electrode configurations to subsurface conditions and help to explain, for example, why the dipole—dipole configuration is so suited to horizontal profiling and the Wenner and Schlumberger configurations to vertical sounding. The spurious response of apparent resistivity curves to near surface lateral resistivity variations is also explained with particular attention being given to the Wenner tripotential configurations.